Turbomachine with evenly cooled turbine shroud

ABSTRACT

In a turbomachine, a turbine shroud surrounding a rotor has an inner wall adjacent the rotor blade tips and additional walls defining an annular chamber. A generally T-shaped baffle with a base portion extending from one of the additional walls and a top portion parallel to the inner wall divides the annular chamber into an annular cooling passage between the top portion and inner wall and a pair of annular manifolds separated from each other by the base portion and open to the annular cooling passage around each axial edge of the top portion. An air inlet is provided into one of the manifolds from a source of air at a high pressure; and an air outlet is provided from the other manifold at a point diametrically opposite the air inlet to a source of air at a lower pressure. The cooling air passes from the first manifold through the cooling passage to the second manifold, and therefore cools the annular wall of the turbine shroud, at all points around the circumference.

United States Patent Liddle Sept. 23, 1975 TURBOMACHINE WITH EVENLY COOLED TURBINE SHROUD [75] Inventor: Sidney G. Liddle, Sterling Heights,

Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Sept. 9, 1974 [21] Appl. No.: 504,034

Primary ExaminerHenry F. Raduazo Attorney, Agent, or Firm-Robert M. Sigler [57] ABSTRACT In a turbomachine, a turbine shroud surrounding a rotor has an inner wall adjacent the rotor blade tips and additional walls defining an annular chamber A generally T-shaped baffle with a base portion extending from one of the additional walls and a top portion parallel to the inner wall divides the annular chamber into an annular cooling passage between the top portion and inner wall and a pair of annular manifolds separated from each other by the base portion and open to the annular cooling passage around each axial edge of the top portion. An air inlet is provided into one of the manifolds from a source of air at a high pressure; and an air outlet is provided from the other manifold at a point diametrically opposite the air inlet to a source of air at a lower pressure. The cooling air passes from the first manifold through the cooling passage to the second manifold, and therefore cools the annular wall of the turbine shroud, at all points around the circumference.

2 Claims, 7 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 3 3,907,458

US Patent Sept. 23,1975 Sheet 2 of3 3,907,458

US Patcnt Sept. 23,1975 Sheet 3 of3 3,907,458

TURBOMACHINE WITH EVENLY COOLE TURBINE SHROUD BACKGROUND OF THE INVENTION not produce work and hence lower efficiency. This gap I should, therefore, be made as small as possible consistent with the differing rates of thermal expansion of the turbine rotor and shroud ring.

In many cases, a cooled shroud ring is useful in controlling the gap width during transient operation. In a simple cooled ring, where an annular chamber is formed in the shroud ring and cooling air from the compressor is introduced at one side of the ring and exhausted at a diametrically opposite point, a temperature gradient exists around the -ring due to heat transferred from the hot gas flowing past the shroud. This temperature gradient causes the ring to deform into an oval or egg shape and result in local variations in the gap width. l

SUMMARY OF THE INVENTION My invention relates to an improved cooled shroud ring which does not change shape as it expands thermally. I accomplish this by including in the annular chamber an annular, generally T-shaped baffle which divides the chamber into a cooling passage between the top of the T and the portion of the shroud ring adjacent the turbine blade tips and a pair of annular manifolds separated from each other by the base of the T and open to the coolingpassage around substantially the full circumference of the baffle.

An inlet is provided for cooling air from the compressor into one manifold and an outlet from the other manifold at a point diametrically opposite the inlet.

Further details and advantages of my invention will be apparent from 'the accompanying drawings and fol-f lowing description of preferred embodiments.

SUMMARY OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a single stage turbine 2 comprising a rotor disk 3 fixed by welding or other means to a shaft 4. This shaft is rotatably mounted by a ball bearing 6 mounted in a shaft housing 7 and held in place by an annular retainer 8 secured to the shaft housing by a ring of cap screws 10.

A turbine nozzle 11 comprises an outer shroud 12, a ring of vanes 14 and an inner shroud 15. The inner shroud is connected to the retainer 8 by a sheet metal ring 16 welded to both. Hot motive fluid gases generated in a combustion apparatus 18, only partially shown, are discharged through an annular outlet 19 of the combustion apparatus into the nozzle 11. The nozzle vanes direct the motive fluid onto blades 20, which may be integral with or fixed to the rotor disk 3, thus driving the turbine 2. The rotor may be connected to a compressor (not illustrated) which supplies air to the combustion apparatus. The turbine 2 may discharge through an annular duct 22 into a further turbine (not illustrated) or into an exhaust. An oil seal 23 engages the'turbine shaft 4. The structure so far described will be recognized by those skilled in the art as conventional in its overall arrangement and will require no further explanation. US. Pat. No. 3,267,674 issued to Coleman et al. on Aug. 23, 1966 discloses an engine of this general type.

The gas flow through turbine blades 20 is confined at the outer diameter of the rotor by a fixed shroud ring 24 located axially of the engine between the rear face of outer shroud 12 and the forward edge of the outer wall 126 of duct 22. Shroud ring 24, in cross section, is seen to comprise an inner wall 27, an outer wall 28, and side walls 30 and 31 which, together, define an enclosed annular passage 32.

Within annular passage 32, a circumferential baffle 34 has one edge fixed to one of walls 28, 30 or 31 and the other axial edge fixed to the midpoint of an annular baffle 35, which extends parallel and adjacent to inner wall 27. Baffles 34 and 35, in cross section, form a generally T-shaped baffle with baffle 34 forming the base thereof and baffle 35 forming the top. In the embodiment of FIG. 1, circumferential'baffle 34 is further divided into a perpendicular portion 36, which joins and is perpendicular to baffle 35, and an.angular portion- 38, which joins perpendicular portion 36 to one of the walls 28, 30 or 31. Angular portion 38 is seen at the top of FIG. 1 to join side wall 31 and to be perpendicular both to side wall 31 and perpendicular portion 36. Moving around the circumference of the shroud ring as in FIG. 2 and looking at sections through the shroud ring, as shown in FIGS. 3 through 6, angular portion 38 is seen to rotate about the perpendicular portion 36, moving across outer wall 28 and then side wall 30 until, at the bottom of FIG. 1 it is seen to be joined and perpendicular to side wall 30. If one were to continue about the circumference of shroud ring 24 in the same direction, one would see this pattern reversed until the top of the shroud ring was once again reached.

Baffles 34 and 35 subdivide enclosed annular passage 32 into an annular cooling passage 39 formed between annular baffle 35 and inner wall 27 and a pair of annular manifolds 40 and 42 which are separated from each other by circumferential baffle 34 but are each open to an opposite axial end of the annular cooling passage 39 around an axial edge of annular baffle 35.

A conduit 43 conducts air from the compressor, not shown, to an air inlet 44, which opens through side wall 30 at the top of shroud ring 24 into annular manifold 40. Another conduit 46 receives air from an air outlet 47 through side wall 30 at the bottom of shroud ring 24 and dumps the air into annular outlet 19. Because of the rotating portion 38 of circumferential baffle 34, air outlet 47 opens from annular manifold 42, even though it is on the same side of shroud ring 24 as air inlet 44.

In operation, pressurized compressor air from conduit 43 passes through air inlet 44 into the top of annular manifold 40. This air flows in both directions around the circumference of annular manifold 40 to the bottom thereof. The only outlet from annular manifold 40 is annular cooling passage 39; and air from around the entire circumference of annular manifold 40 thus flows around the edge of annular baffle 35 and axial across annular cooling passage 39. At the other axial end of passage 39, the air flows around the other axial edge of annular baffle 35 into annular manifold 42. The air then flows from whatever point it enters annular manifold 42 around the circumference thereof to air outlet 47, from which it flows through conduit 46 to annular outlet 19, which is at a lower pressure than the compressor. In annular outlet 19 the air joins the air from the combustion apparatus 18 and passes through the turbine nozzle to help turn turbine 2.

Another embodiment of my invention is shown in FIG. 7. This embodiment is substantially the same of that shown in FIGS. 1-6, except that the air from the air outlet is dumped into annular duct 22, so that air outlet 48 is formed through side wall 31 of shroud ring 24 and communicates with annular duct 22 through a conduit 50, a supplementary manifold 51 and a plurality of small angled openings 52 through outer wall 26. The purpose of the supplementary manifold 51 and angled openings 52 is to reduce flow disturbances caused by air entering the main stream of air flowing into the power turbine nozzles on those engines where a power turbine is included; and these parts would obviously not be needed if no such power turbine were present.

Since outlet opening 48 is formed through the opposite side wall 31 of shroud ring 24 from the side wall 30 containing the air inlet 44, a simpler circumferential baffle 54 can be used. Circumferential baffle 54 extends perpendicularly inward from the outer wall 28 to form the base of a pure T-shaped baffle, with annular baffle 35 forming the top. The shape and direction of circumferential baffle 54 are unchanging around the circumference, unlike that of circumferential baffle 34. This, of course, makes shroud ring 24 simpler and less expensive to manufacture; however, in this embodiment the cooling air is dumped on the downstream side of turbine 2 so that it does not help power turbine 2.

Naturally, the source of the cooling air, the point where the cooling air is dumped, the axial side of the shroud ring on which the air inlet and outlet are located, and the particular shape of circumferential baffie 34 or 54 can be varied at will within the scope of my invention, depending upon the design factors of a particular turbomachine. Equivalent embodiments will occur to those skilled in the art, and my invention should thus be limited only by the claims which follow.

I claim:

1. In a turbomachine having a turbine rotor with a plurality of radial blades, a first source of air at greater than atmospheric pressure and a second source of air at a pressure lower than that of the first air source: a turbine shroud ring surrounding the turbine rotor and having an inner wall adjacent the tips of the blades, the turbine shroud defining an annular coolant passage, the turbine shroud including a baffle effective to divide the coolant passage into an annular passage adjacent the inner wall and a pair of annular manifolds separated by the passage from the inner wall, each of the manifolds being separated from the other but open to the annular passage substantially around their circumference, the shroud ring further including an air inlet communicating the first air source to one of the manifolds and an air outlet diametrically opposite the air inlet communicating the other manifold with the second air source.

2. In a turbomachine including a rotor having a plurality of radial blades, a first source of air at greater than atmospheric pressure and a second source of air at a pressure less than that of the first air source: a tur bine shroud ring surrounding the rotor and having an inner wall adjacent the tips of the blades, the turbine shroud ring further comprising additional walls defining an annular coolant passage, a circumferential baffle projecting into the coolant passage from the additional walls and an annular baffle adjacent the inner wall and joined to the inner edge of the circumferential baffle, the annular baffle and inner wall defining a passage therebetween, the circumferential baffle, annular baffie and additional walls defining a pair of annular manifolds separated from each other by the circumferential baffle and open to the passage around substantially the full circumference ofthe two axial edges of the annular baffle, the shroud ring further comprising an air inlet between the first air source and one of the manifolds and an air outlet diametrically opposite the air inlet between the other manifold and the second air source. 

1. In a turbomachine having a turbine rotor with a plurality of radial blades, a first source of air at greater than atmospheric pressure and a second source of air at a pressure lower than that of the first air source: a turbine shroud ring surrounding the turbine rotor and having an inner wall adjacent the tips of the blades, the turbine shroud defining an annular coolant passage, the turbine shroud including a baffle effective to divide the coolant passage into an annular passage adjacent the inner wall and a pair of annular manifolds separated by the passage from the inner wall, each of the manifolds being separated from the other but open to the annular passage substantially around their circumference, the shroud ring further including an air inlet communicating the first air source to one of the manifolds and an air outlet diametrically opposite the air inlet communicating the other manifold with the second air source.
 2. In a turbomachine including a rotor having a plurality of radial blades, a first source of air at greater than atmospheric pressure and a second source of air at a pressure less than that of the first air source: a turbine shroud ring surrounding the rotor and having an inner wall adjacent the tips of the blades, the turbine shroUd ring further comprising additional walls defining an annular coolant passage, a circumferential baffle projecting into the coolant passage from the additional walls and an annular baffle adjacent the inner wall and joined to the inner edge of the circumferential baffle, the annular baffle and inner wall defining a passage therebetween, the circumferential baffle, annular baffle and additional walls defining a pair of annular manifolds separated from each other by the circumferential baffle and open to the passage around substantially the full circumference of the two axial edges of the annular baffle, the shroud ring further comprising an air inlet between the first air source and one of the manifolds and an air outlet diametrically opposite the air inlet between the other manifold and the second air source. 